Magnetic device

ABSTRACT

A magnetic device comprises a magnetic element, a first magnetic field application device, and a second magnetic field application device. The first and second magnetic field applying means are disposed on mutually opposite sides of the magnetic element. The magnetic element is, for example, an element in which a soft magnetic film is formed in a meandering shape on a nonmagnetic substrate. The first and second magnetic field application device create a magnetic field in one direction from the first magnetic field application device toward the second magnetic field application device. The bias magnetic field in one direction is thereby applied to the entire soft magnetic film in the magnetic element disposed between the first and second magnetic field application device.

TECHNICAL FIELD

The present invention relates to a magnetic device that is provided witha magnetic sensor.

BACKGROUND ART

In recent years, in order to cut costs and reduce chip components,devices have been proposed in which induction elements such as magneticimpedance elements are integrated on substrates such as semiconductors.When magnetic impedance elements of this type are used for a magneticsensor, it is necessary to apply a bias magnetic field to the magneticimpedance elements due to the characteristics of impedance change.

A method that may be considered in order to apply a bias magnetic fieldto the magnetic impedance elements is, for example, to place magnetsadjacent to the magnetic impedance elements (See Japanese PatentApplication Laid-Open (JP-A) No. 2002-43649). However, applying a biasmagnetic field by means of magnets in this manner poses various problemswhen applied to magnetic sensors as the magnetic field strength of theindividual magnets is not uniform, and it is difficult to consistentlyapply a bias magnetic field having a constant value.

In contrast, a method of consistently applying a bias magnetic fieldhaving a uniform strength to magnetic impedance elements is known inwhich a spiral-shape or coil-shape conductive layer is formed adjacentto the magnetic impedance elements, and a bias magnetic field isgenerated by energizing this conductive layer (Japanese PatentApplication Laid-Open (JP-A) No.2001-221838). Because a magnetic sensorin which magnetic impedance elements are arranged along a coil centeraxis of a conductive layer formed in a coil shape, in particular, hasthe characteristic that it is possible to apply a strong bias magneticfield consistently to the magnetic impedance elements, this method ispreferable as it enables highly accurate magnetic sensors to beobtained.

However, in order to apply a bias magnetic field to the magneticimpedance elements, when a coil-shape magnetic field application deviceis formed around the impedance elements so as to envelop the magneticimpedance elements, the outer configuration of the overall magneticdevice is enlarged by this coil, so that the problem has arisen thatthis has prevented any size reduction or slenderization of anyinstrument in which this magnetic device is mounted.

SUMMARY OF INVENTION

Exemplary embodiments of the present invention were conceived in view ofthe above described circumstances, and to provide a magnetic device thatis provided with magnetic elements that can be manufactured with a smallsize and weight and at low cost. However, exemplary embodiments of thepresent invention need not solve these or any other programs.

A first aspect of the present invention is a magnetic device thatincludes: a magnetic element; and a first magnetic field applicationdevice and a second magnetic field application device that are placed soas to sandwich the magnetic element, and that are used to apply aunidirectional bias magnetic field to the magnetic element.

A second aspect of the present invention is the magnetic deviceaccording to the first aspect in which the first magnetic fieldapplication device and the second magnetic field application device eachinclude an independent magnetic field generating device and anindependent magnetic field induction device.

A third aspect of the present invention is the magnetic device accordingto the first aspect in which the magnetic field induction devices ofboth the first magnetic field application device and the second magneticfield application device, and the magnetic element are placed onsubstantially the same plane.

A fourth aspect of the present invention is a magnetic device thatincludes: a first substrate having a first conductive layer and a secondconductive layer; a second substrate having a third conductive layer anda fourth conductive layer; a magnetic element that is placed between thefirst substrate and the second substrate; a first connecting portionthat electrically connects the first conductive layer and the thirdconductive layer; a second connecting portion that electrically connectsthe second conductive layer and the fourth conductive layer; acoil-shaped first magnetic field generating device that includes thefirst conductive layer, the third conductive layer, and the firstconnecting portion; a coil-shaped second magnetic field generatingdevice that includes the second conductive layer, the fourth conductivelayer, and the second connecting portion; a first magnetic fieldinduction device that passes through the center of the coil shape of thefirst magnetic field generating device; and a second magnetic fieldinduction device that passes through the center of the coil shape of thesecond magnetic field generating device.

A fifth aspect of the present invention is the magnetic device accordingto the fourth aspect in which there is further provided a thirdsubstrate that is placed between the first substrate and the secondsubstrate, and the third substrate has a magnetic element housingportion that houses the magnetic element, a first housing portion thathouses the first magnetic field induction device, and a second housingportion that houses the second magnetic field induction device, and themagnetic element housing portion is placed between the first housingportion and the second housing portion.

According to exemplary embodiments the magnetic device according to thepresent invention, as a result of the first magnetic field applicationdevice and the second magnetic field application device being placed onboth sides of the magnetic element, it is possible to apply a strongbias magnetic field to the magnetic element that is efficientunidirectionally, and it is possible to achieve a highly accuratemagnetic sensor.

In addition, a magnetic field generating device that is used to apply abias magnetic field to a magnetic element can be located away from themagnetic element. Because of this, it is not necessary to form themagnetic field generating device in proximity to the magnetic element.As a result, it is possible to achieve reductions in the size, andparticularly in the thickness of the overall magnetic device, and it ispossible to improve the degree of freedom in the layout of theinstrument on which the magnetic device is mounted.

Exemplary embodiments of the present invention may have the abovediscussed advantages. However, embodiments of the present invention neednot have any advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] FIG. 1 is a perspective view showing an exemplary embodiment ofthe magnetic device according to the present invention.

[FIG. 2] FIG. 2 is a perspective view showing another exemplaryembodiment of the magnetic device according to the present invention.

[FIG. 3] FIG. 3 is an exploded perspective view showing anotherexemplary embodiment of the magnetic device according to the presentinvention.

[FIG. 4] FIG. 4 is an explanatory view showing the magnetic fieldapplication device shown in FIG. 3.

[FIG. 5] FIG. 5 is an exploded perspective view showing anotherexemplary embodiment of the magnetic device according to the presentinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

An embodiment of the magnetic device according to the present inventionwill now be described based on the drawings. Note that the presentinvention is not limited to this embodiment. FIG. 1 is a perspectiveview showing an exemplary embodiment of the magnetic device (i.e.,magnetic sensor) according to the present invention. A magnetic device10 of the present invention is provided with a magnetic element 11, anda first magnetic field application device 12 and second magnetic fieldapplication device 13 that are positioned so as to sandwich the magneticelement 11.

The magnetic element 11 is obtained, for example, by forming a softmagnetic film 11 b in a meandering pattern on a surface of anon-magnetic substrate 11 a. The first magnetic field application device12 and second magnetic field application device 13 form a magnetic fieldM traveling in one direction S from the first magnetic field applicationdevice 12 towards the second magnetic field application device 13. As aresult, in the magnetic element 11 that is located between the firstmagnetic field application device 12 and the second magnetic fieldapplication device 13, the bias magnetic field M traveling in the onedirection is applied to the entire soft magnetic film 11 b.

According to the magnetic device 10 having this structure, as a resultof the first magnetic field application device 12 and the secondmagnetic field application device 13 being placed on both sides of themagnetic element 11, it is possible to apply a strong bias magneticfield to the magnetic element 11 that is efficient in the one direction,and it is possible to achieve a highly accurate magnetic sensor.

In addition, because a magnetic field generating device that is used toapply a bias magnetic field to the magnetic element 11 can be locatedaway from the magnetic element 11, it is not necessary to form themagnetic field generating device in proximity to the magnetic element.As a result, it is possible to achieve reductions in the size, andparticularly in the thickness of the overall magnetic device 10, and itis possible to improve the degree of freedom in the layout of theinstrument on which the magnetic device 10 is mounted.

The first magnetic field application device 12 and the second magneticfield application device 13 may also each be formed from an independentmagnetic field generating device and an independent magnetic fieldinduction device. The first magnetic field application device 12 has afirst magnetic field generating device 15 and a first magnetic fieldinduction device 16. The second magnetic field application device 13 hasa second magnetic field generating device 17 and a second magnetic fieldinduction device 18.

Both ends of the first magnetic field generating device 15 and thesecond magnetic field generating device 17 are connected, for example,to a power supply 14, and may be formed by an inductor that is wound ina coil shape. The first magnetic field induction device 16 and thesecond magnetic field induction device 18 may be formed, for example, byarranging a high permeability material which is formed in a ribbon shape(i.e., in a thin belt shape) such that it passes through a center axis Pof the respective coil shapes of the first magnetic field generatingdevice 15 and the second magnetic field generating device 17.

Ends 16 a and 18 a on one side of the first magnetic field inductiondevice 16 and the second magnetic field induction device 18 which areformed in this ribbon shape (i.e., a thin belt shape) extend topositions adjacent to the magnetic element 11. Ends 16 b and 18 b on theother side of the first magnetic field induction device 16 and thesecond magnetic field induction device 18 are formed as open magneticcircuits in order to detect changes in the external magnetic field inthe magnetic element 11.

In this manner, by forming the first magnetic field application device12 and the second magnetic field application device 13 each from anindependent magnetic field generating device and an independent magneticfield induction device, when a solenoid coil, for example, is used forthe magnetic field application device, it is sufficient for the firstmagnetic field generating device 15 and the second magnetic fieldgenerating device 17, which are small-sized coils, to be formed so as toenvelop the first magnetic field induction device 16 and the secondmagnetic field induction device 18, which are formed from a thin, highpermeability material in a ribbon shape, without having to form in thevicinity of the magnetic element a coil, which is a magnetic fieldgenerating device, such that it envelops the comparatively large-sizedmagnetic element 11. Accordingly, it is possible to achieve a reductionin the thickness of the magnetic device 10.

Moreover, by extending the one ends 16 a and 18 a of the first magneticfield induction device 16 and the second magnetic field induction device18 to positions adjacent to the magnetic element 11, even if the firstmagnetic field generating device 15 and the second magnetic fieldgenerating device 17 are formed at positions away from the magneticelement 11, it is possible for a bias magnetic field generated by thesemagnetic field generating devices 15 and 17 to be applied to themagnetic element 11 without being attenuated by the first magnetic fieldinduction device 16 and the second magnetic field induction device 18.

For the high permeability material constituting the first magnetic fieldinduction device 16 and the second magnetic field induction device 18,it is possible to use, for example, a cobalt-based amorphous thin ribbonor a sintered ferrite thin film or the like. In particular, if acobalt-based amorphous thin ribbon which has pliability is used for thefirst magnetic field induction device 16 and the second magnetic fieldinduction device 18, then because it is possible to place the firstmagnetic field generating device 15 and the second magnetic fieldgenerating device 17 in positions away from the magnetic element 11, andinduce a bias magnetic field in the magnetic element 11 by freelybending the first magnetic field induction device 16 and the secondmagnetic field induction device 18, it becomes possible to arrange themagnetic device 10 in an unrestricted layout in accordance with theshape of the instrument in which the magnetic device 10 is incorporated.

The first magnetic field induction device 16 and second magnetic fieldinduction device 18 and the magnetic element 11 may be placed on asubstantially identical plane F. By placing the magnetic field inductiondevices 16 and 18 and the magnetic element 11 on substantially the sameplane F, the bias magnetic field generated by the first magnetic fieldgenerating device 15 and the second magnetic field generating device 17can be efficiently applied in the direction of the magnetic element 11while any attenuation thereof is suppressed, thereby enabling a highlysensitive magnetic element 11 to be obtained.

In the above described embodiment, a coil-shaped inductor which isconnected to a power supply, namely, an electromagnet is used for themagnetic field generating devices, however, in addition to this it isalso possible to use permanent magnets or the like for the magneticfield generating devices.

FIG. 2 is a perspective view showing another exemplary embodiment of themagnetic device (i.e., magnetic sensor) according to the presentinvention. A magnetic device 20 of this embodiment is provided with afirst magnetic field application device 22 and a second magnetic fieldapplication device 23 which are placed so as to sandwich a magneticelement 21. The first magnetic field application device 22 is formedindependently from a first magnetic field generating device 24 and afirst magnetic field induction generating device 25, while the secondmagnetic field application device 23 is formed independently from asecond magnetic field generating device 26 and a second magnetic fieldinduction generating device 27.

The first magnetic field generating device 24 and the second magneticfield generating device 26 are formed by permanent magnets, for example,made of NdFeB or SmCo or the like. A bias magnetic field generated bythese permanent magnets is inducted to the magnetic element 21 by meansof the first magnetic field induction generating device 25 and thesecond magnetic field induction generating device 27, so that aunidirectional bias magnetic field is applied to the magnetic element21. By using permanent magnets for the first magnetic field generatingdevice 24 and the second magnetic field generating device 26, it ispossible to generate a bias magnetic field without having to supplyelectricity. Because of this, compared with a magnetic device which usesa solenoid coil or the like, it is possible to simplify the structure,and achieve reductions in both size and weight.

Next, a description will be given of an exemplary embodiment of themagnetic device according to the present invention is formed into apackage having a multilayer structure. FIG. 3 is an exploded perspectiveview showing another exemplary embodiment of the magnetic deviceaccording to the present invention. A magnetic device 30 has a firstsubstrate 31, a second substrate 32, a magnetic element 34 which issandwiched between the first substrate 31 and the second substrate 32,and a first magnetic field induction device 48 and a second magneticfield induction device 49 which are placed so as to sandwich themagnetic element 34 from both sides thereof. It is also possible for adriver chip 35 to be placed between the first substrate 31 and thesecond substrate 32, and for a third substrate 33 to be provided tohouse the magnetic element 34 and the driver chip 35.

First conductive layers 41, second conductive layers 42, and extractionconductive layers 45 are formed on a surface 31 a of the first substrate31. Third conductive layers 43 and fourth conductive layers 44 areformed on a surface 32 a of the second substrate 32. The magneticelement 34 is obtained, for example, by forming a soft magnetic film 34b in a meandering pattern on a surface of a non-magnetic substrate 34 a,and electrode pads 46 a and 46 b are formed on both ends of the softmagnetic film 34 b. When a bias magnetic field is applied to thismagnetic element 34, output signals therefrom are changed in accordancewith the strength of the magnetic field.

Moreover, the driver chip 35 is an integrated circuit that controls themagnetic element 34, and electrode pads 47 a and 47 b are formed on asurface thereof. A first non-conductive layer 54, and a secondnon-conductive layer 55 that insulate the first magnetic field inductiondevice 48 and the second magnetic field induction device 49 from thethird conductive layers 43 and the fourth conductive layers 44 areformed respectively on the second substrate 32 side of the firstmagnetic field induction device 48 and the second magnetic fieldinduction device 49.

Third connecting portions 53 which are formed from conductive paste orcopper plating or the like that penetrate from the one surface 31 a tothe other surface 31 b of the first substrate 31 and electricallyconnect the extraction conductive layers 45 respectively to theelectrode pads 46 a and 46 b of the magnetic element 34 and electrodepads 47 a and 47 b of the driver chip 35 are formed in the firstsubstrate 31.

In the third substrate 33, there are provided (i) a magnetic elementhousing portion 36 a that houses the magnetic element 34, (ii) a chiphousing portion 36 b that houses the driver chip 35, (iii) a firsthousing portion 36 c that houses the first magnetic field inductiondevice 48, and (iv) a second housing portion 36 d that houses the secondmagnetic field induction device 49.

In addition, first connecting portions 51 which are formed fromconductive paste that penetrate from one surface 33 a to another surface33 b of the third substrate 33 and electrically connect the firstconductive layers 41 to the second conductive layers 43 are formed inthe third substrate 33, and second connecting portions 52 which areformed from conductive paste that penetrate from one surface 33 a toanother surface 33 b of the third substrate 33 and electrically connectthe second conductive layers 42 to the fourth conductive layers 44 areformed in the third substrate 33.

As a result of the first conductive layers 41 and the third conductivelayers 43 being electrically connected by the first connecting portions51, and the second conductive layers 42 and the fourth conductive layers44 being electrically connected by the second connecting portions 52 inthis manner, as is shown in typical view in FIG. 4, a coil-shaped firstmagnetic field generating device 57 that envelops the periphery of thefirst magnetic field induction device 48, and a coil-shaped secondmagnetic field generating device 58 that envelops the periphery of thesecond magnetic field induction device 49 are formed respectively. Afirst magnetic field application device 61 is formed by the firstmagnetic field generating device 57 and the first magnetic fieldinduction device 48, and a second magnetic field application device 62is formed by the second magnetic field generating device 58 and thesecond magnetic field induction device 49.

Furthermore, by respectively energizing the electrode pads 57 a and 57 bat both ends of the first magnetic field generating device 57 and theelectrode pads 58 a and 58 b at both ends of the second magnetic fieldgenerating device 58, magnetic fields are generated in the firstmagnetic field generating device 57 and the second magnetic fieldgenerating device 58. The magnetic fields which are generated in thefirst magnetic field generating device 57 and the second magnetic fieldgenerating device 58 are inducted to the magnetic element 34respectively by the first magnetic field induction device 48 and thesecond magnetic field induction device 49. As a result, aunidirectional, strong bias magnetic field M is applied to the magneticelement 34.

According to the magnetic device 30 having the above describedstructure, the first magnetic field generating device 57 and the secondmagnetic field generating device 58 are formed respectively in a compactcoil shape so as to sandwich the magnetic element 34 from both sideswhile being isolated therefrom, and the bias magnetic fields which aregenerated by this first magnetic field generating device 57 and secondmagnetic field generating device 58 can be inducted by the firstmagnetic field induction device 48 and the second magnetic fieldinduction device 49 without being attenuated thereby, and applied to themagnetic element 34. Accordingly, it is possible to achieve a small,lightweight magnetic device that can be manufactured at low cost.

The first substrate 31 may be formed from a nonconductive resin such as,for example polyimide. The first conductive layer 41, the secondconductive layers 42, and the extraction conductive layers 45 which areformed on the first substrate 31 may also be formed on the other surface31 b on the opposite side from the one surface 31 a of the firstsubstrate 31. The first conductive layers 41, the second conductivelayers 42, and the extraction conductive layers 45 may be formed from amaterial having superior conductivity such as, for example, copper,aluminum, gold, or the like.

It is sufficient if the soft magnetic film 34 b that makes up themagnetic element 34 is, for example, an amorphous soft magneticmaterial. Moreover, provided that the shape of the soft magnetic film 34b is one that makes it possible to detect magnetism with a high degreeof accuracy, then any type of shape may be used in addition to ameandering shape. The first connecting portions 51, the secondconnecting portions 52, and the third connecting portions 53 may be aconductive paste which is formed by dispersing a fine powder ofconductive metal in an adhesive medium. For the first magnetic fieldinduction device 48 and the second magnetic field induction device 49,it is possible to use, for example, a cobalt-based amorphous thin ribbonor a sintered ferrite thin film or the like.

In the above described embodiment, the first substrate 31 and the secondsubstrate 32 are joined so as to sandwich the third substrate 33 usingthe first connecting portions 51 and the second connecting portions 52which are formed from the aforementioned adhesive conductive paste,however, in addition to this it is also possible to employ a structurein which the respective layers are joined together by forming adhesivelayers using an adhesive agent or the like between the first substrate31 and the third substrate 33, and between the third substrate 33 andthe second substrate 32.

The second substrate 32 may be formed from a nonconductive resin suchas, for example, polyimide. The third conductive layers 43 and thefourth conductive layers 44 which are formed on the second substrate 32may also be formed on the other surface 32 b on the opposite side fromthe one surface 32 a of the second substrate 32. The third conductivelayers 43 and the fourth conductive layers 44 may be formed from amaterial having superior conductivity such as, for example, copper,aluminum, gold, or the like.

In an example in which the above described magnetic device is formedinto a package having a multilayer structure as well, it is alsopossible to use magnets as the magnetic field generating device. FIG. 5is an exploded perspective view showing another exemplary embodiment ofthe magnetic device according to the present invention. In thisembodiment, a magnetic device 70 has a first substrate 71, a secondsubstrate 72, a magnetic element 73 which is sandwiched between thefirst substrate 71 and the second substrate 72, and a first magneticfield application device 74 and a second magnetic field applicationdevice 75 which are placed so as to sandwich the magnetic element 73from both sides thereof.

The first magnetic field application device 74 is formed by the firstmagnetic field generating device 76 and the first magnetic fieldinduction device 77. The second magnetic field application device 75 isformed by the second magnetic field generating device 78 and the secondmagnetic field induction device 79. In addition, permanent magnets areused for the first magnetic field generating device 76 and the secondmagnetic field generating device 78.

As a result, the bias magnetic fields which are generated by the firstmagnetic field generating device 76 and second magnetic field generatingdevice 78, which are permanent magnets, can be applied to the magneticelement 73 by the first magnetic field induction device 77 and thesecond magnetic field induction device 79 without being attenuatedthereby. By using magnets as magnetic field generating devices in thismanner, it is possible to generate a bias magnetic field without havingto supply electricity. Because of this, compared with a magnetic devicewhich uses a solenoid coil or the like, it is possible to simplify thestructure, and achieve reductions in both size and weight of themagnetic device 70.

EXAMPLES

The effects of the magnetic field induction device constructed from ahigh permeability magnetic material of the present invention weretested. In a magnetic device such as that shown in FIG. 1, a film ofCoZrNb was formed in a meandering pattern on a Si substrate having achip size of 2.5 mm×1.2 mm×625 μm so as to provide a magnetic element.The bias magnetic field of this magnetic element was 8 (Oe). Aribbon-shaped cobalt-based amorphous alloy having a width ofapproximately 1 mm and a thickness of 20 μm was used for the magneticfield induction devices. 0.2 A of current was supplied to coil-shapedmagnetic field application devices having 120 turns in the coil. Thespacing between end portions of the magnetic field induction devices andthe magnetic element was 1 mm. The strengths of the bias magnetic fieldsapplied to the magnetic element when one magnetic field induction devicein the form of a ribbon-shaped cobalt-based amorphous alloy was used,and when three magnetic field induction devices in the form ofribbon-shaped cobalt-based amorphous alloys were stacked, and when nomagnetic field induction device was formed (in order to provide acomparative example) were measured. The results of this test are shownin Table 1.

TABLE 1 Number of ribbons Magnetic field strength (Oe) 0 (Comparativeexample) 2.5 1 6 3 12

According to the results shown in Table 1, it was confirmed that it ispossible to increase the strength of the bias magnetic field that isapplied to a magnetic element by forming a magnetic field inductiondevice. It was also confirmed that it is possible to increase thestrength of the bias magnetic field by increasing the number of magneticfield induction devices.

1. A magnetic device comprising: a first substrate having a firstconductive layer and a second conductive layer; a second substratehaving a third conductive layer and a fourth conductive layer; amagnetic element that is placed between the first substrate and thesecond substrate; a first connecting portion that electrically connectsthe first conductive layer and the third conductive layer; a secondconnecting portion that electrically connects the second conductivelayer and the fourth conductive layer; a coil-shaped first magneticfield generating device that includes the first conductive layer, thethird conductive layer, and the first connecting portion; a coil-shapedsecond magnetic field generating device that includes the secondconductive layer, the fourth conductive layer, and the second connectingportion; a first magnetic field induction device that passes through thecenter of the coil shape of the first magnetic field generating device;a second magnetic field induction device that passes through the centerof the coil shape of the second magnetic field generating device; and athird substrate that is placed between the first substrate and thesecond substrate, and the third substrate has a magnetic element housingportion, which houses the magnetic element, a first housing portion,which houses the first magnetic field induction device, and a secondhousing portion, which houses the second magnetic field inductiondevice, and wherein the magnetic element housing portion is placedbetween the first housing portion and the second housing portion.
 2. Themagnetic device according to claim 1, wherein at least one of the firstmagnetic field generating device and the second magnetic fieldgenerating device is a permanent magnet.
 3. The magnetic deviceaccording to claim 1, wherein at least one of the first magnetic fieldinduction device and the second magnetic field induction device is acobalt-based thin ribbon.
 4. The magnetic device according to claim 1,wherein at least one of the first magnetic field induction device andthe second magnetic field induction device is a sintered ferrite thinfilm.
 5. The magnetic device according to claim 1, wherein at least oneof the first conductive layer and the second conductive layer is formedfrom a material at least one of copper, aluminum and gold.
 6. Themagnetic device according to claim 1, further comprising a thirdsubstrate placed between the first substrate and the second substrate;wherein said third substrate includes a magnetic element housingportion.
 7. The magnetic device according to claim 1, wherein each ofsaid first and second substrates are surrounded by each of theconnecting portions and each of the conductive layers.